The course of development of magnetic data storage disk drives has proceeded in two generally divergent directions. A first line of development has been of rigid magnetic disks rotated in juxtaposition to magnetic read/write heads disposed very closely to the disk so that they "fly" on an air bearing in very close proximity to the disk. The close proximity allows high data densities, but the rigid disks are expensive and delicate to manufacture. A second line of development has been the so-called "floppy" disk in which a non-rigid disk is rotated, typically within an envelope. This sort of disk, not being rigid, cannot be rotated in close juxtaposition to such a flying head and accordingly data densities are lower.
It has previously been proposed to rotate a flopply disk in close proximity to a fixed, flat "Bernoulli" plate. The thin layer of air between the disk and the plate tends to rotate with the disk and to be thrown outwardly by centrifugal force. This creates a vacuum between plate and disk which tends to pull the disk close to the plate and cause it to behave in a substantially rigid manner. A flying head of the type described above as used in conjunction with rigid disks can then be used, providing the advantage of high data density but without the expense associated with rigid magnetic disks.
The prior art teaches that it is desirable to somehow texturize or break up the surface of the Bernoulli plates, so that the magnetic media will not cling to the surface, or "ring", as with a perfectly smooth plate. Several methods of texturing the surface have previously been disclosed, however, none have provided appropriate performance together with inexpensive processing of the plate. In particular, the texturing must proceed in such a manner that there are no projecting burrs or scratches on its surface. Since the disk is so close to the plate the height of the projections need not be substantial to severely damage the magnetic media.